class_docstr: Pan-zoom transform
  
  Parameters
  ----------
  canvas : instance of Canvas | None
      The canvas to attch to.
  aspect : float | None
      The aspect ratio to apply.
  **kwargs : dict
      Keyword arguments to pass to the underlying `STTransform`.
docstr: Resize handler
  
  Parameters
  ----------
  event : instance of Event
      The event.
docstr_tok: ["Resize","handler","Parameters","--","--","--","--","--","event",":","instance","of","Event","The","event","."]
code: def on_resize(self, event):
      """Resize handler
  
      Parameters
      ----------
      event : instance of Event
          The event.
      """
      if self._aspect is None:
          return
      w, h = self._canvas.size
      aspect = self._aspect / (w / h)
      self.scale = (self.scale[0], self.scale[0] / aspect)
      self.shader_map()
  
file_path: vispy/vispy/visuals/transforms/interactive.py
imports: from __future__ import division
  import numpy
  from .linear import STTransform
label_desc: Use image node_id 4 for calling the PanZoomTransform obj's underlying member method code with example usage: obj.on_resize(event) without return types